Australopithecus is an extinct genus of the family hominidae, order primates, that lived in eastern and southern Africa about 2 to 4 million years ago. This hominid is regarded by paleontologists as being ancestral to the genus Homo and transitional between ancestral apes and humans. Species of the genus include Australopithecus anamensis (about 4 million years ago), Australopithecus afarensis (3.9 to 2.9 million years ago), and Australopithecus africanus (2-3 million years ago) and used to include species now classified in the genus Paranthropus such as P. robustus and P. boisei, also Australopithecus sediba.

Perhaps the most famous australopithecine is Lucy, a 40 percent complete A. afarensisfossilized skeleton about 3.2 million years old discovered by Donald Johanson in 1973. The Laetoli footprints, discovered by Mary Leakey in Tanzania in 1976, are believed to be the 3.6 million-year-old traces of two or three A. afarensis individuals preserved in volcanic ash.

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The brain size of A. afarensis was about 400 cc, much smaller than that of a human. Its skull had characteristics common to an ape's, although the crowns of the teeth were small like a human's. As with apes, males of the species, at about four feet tall, were significantly larger than females. The arms and fingers were between the length of an ape's and a human's.

A. afarensis was obviously bipedal as evidenced by its lower skeletal structure, which strongly resembles that of a human. In particular the construction of the pelvic girdle, neck of the femur, knee joint and thigh bone arrangement, and heel bone indicates bipedal locomotion. This conclusion is confirmed by analysis of the shape of the footprints preserved at Laetoli.

The Institute for Creation Research deals with the problem of the transitional nature of the australopithecines by denying that they were bipedal. In their publication Acts & Facts they note, "Australopithecus, in the view of some leading evolutionists, was not intermediate between ape and man and did not walk upright,"[2] and cite the counter-consensus opinion of Charles Oxnard.

Jack Chick's answer is to claim that "most experts now agree Lucy was an unusual chimpanzee not a missing link."[3]